The term thermal runaway event refers to an uncontrolled increase in temperature in a battery system. During a thermal runaway event, the generation of heat within a battery system or a battery cell exceeds the dissipation of heat, thus leading to a further increase in temperature. A thermal runaway event may be triggered by various conditions, including a short circuit within the cell, improper cell use, physical abuse, manufacturing defects, or exposure of the cell to extreme external temperatures.
A battery system may comprise a plurality of battery cells in relatively close proximity to one another. Various cooling systems may be designed to prevent the spread of heat from a cell experiencing a runaway thermal event to adjacent cells, since exposure of a battery cell to high temperature may cause the cell to experience a thermal runaway event.
The inventors of the present application have recognized that certain advantages may be realized by providing a secondary “cooling” system that may be used to contain a thermal runaway event and also operates passively (e.g., when the main cooling system is switched off, damaged, etc.). The present disclosure provides various embodiments of such a system and related methods. Use of a passive system may help to ensure reliable operation of the cooling system regardless of the other conditions that may have triggered the thermal event.